---更新最终过期时间戳-秒
return [[
    local key = KEYS[1]
    local sec = tonumber(KEYS[2])
    local dif = tonumber(redis.call("TTL", key))
    if dif == -2 then
        ---key 不存在
        return -1
    elseif dif >= 0 then
        local now = tonumber(redis.call("TIME")[1])
        local cif = sec - now
        if cif <= dif then
            return -1 
        end
    end
    return redis.call("EXPIREAT", key, sec)
]]
